CVE-2026-55700 in pnpm
Summary
by MITRE • 06/25/2026
pnpm is a package manager. From 11.3.0 until 11.5.3, `pnpm stage download` derived a local filename from registry-controlled package name and version fields. A crafted manifest could escape the selected download directory and overwrite another reachable file. The merged fix validates both fields, derives one safe filename, and verifies the final destination before writing. This vulnerability is fixed in 11.5.3.
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Analysis
by VulDB Data Team • 07/07/2026
The pnpm package manager experienced a critical path traversal vulnerability in versions 11.3.0 through 11.5.3 that affected the `pnpm stage download` command functionality. This vulnerability stemmed from inadequate input validation during the filename derivation process, where the system relied on registry-controlled package name and version fields to construct local filenames. The flaw created a condition where maliciously crafted package manifests could manipulate the filename generation logic to escape the intended download directory boundaries.
The technical implementation of this vulnerability involved the command's failure to properly sanitize or validate the package name and version fields obtained from remote registries before using them to construct filesystem paths. When these fields contained specially crafted characters or sequences, they could potentially traverse directory structures and overwrite files in locations outside the designated staging area. This behavior directly aligns with common path traversal attack patterns documented in CWE-23, which describes improper limitation of a pathname to a restricted directory.
The operational impact of this vulnerability extended beyond simple file overwrites, as it created potential for arbitrary file system modifications within the context of the pnpm process execution environment. Attackers could leverage this weakness to modify critical system files, inject malicious code into existing packages, or disrupt normal package management operations. The vulnerability particularly affected environments where pnpm was used with untrusted registries or where package integrity could not be fully verified, creating opportunities for supply chain attacks that align with ATT&CK technique T1195.002 for supply chain compromises.
The fix implemented in version 11.5.3 addressed the vulnerability through multiple validation layers including input sanitization of both name and version fields, implementation of a secure filename derivation algorithm that prevented path traversal sequences, and additional verification of the final destination path before any file operations occurred. This approach follows security best practices for preventing directory traversal attacks by ensuring that all user-controlled inputs are properly validated and normalized before being used in filesystem operations. The mitigation strategy demonstrates proper defense-in-depth principles by combining input validation with output verification to create a robust protection mechanism against similar classes of vulnerabilities.
The vulnerability highlights the importance of validating all data sources when constructing filesystem paths, particularly in package managers where external registry data is processed. It underscores the necessity of implementing strict path validation and sanitization processes for any system that derives filesystem operations from remote or untrusted sources. Organizations using pnpm should ensure immediate upgrades to version 11.5.3 or later to prevent exploitation of this vulnerability while maintaining proper security hygiene practices around package management workflows. The fix represents a complete remediation approach that addresses both the root cause and potential attack vectors, providing comprehensive protection against similar path traversal scenarios in future implementations.
This vulnerability serves as a reminder of the critical security considerations in package management systems where trust boundaries between local and remote data sources must be carefully enforced. The implementation of proper input validation and secure file system operations remains essential for preventing privilege escalation and arbitrary code execution scenarios that could compromise entire development environments or production systems relying on such package managers.